HVAC system with volume modulating valve

ABSTRACT

An HVAC system is described having components of a variable refrigerant flow (VRF) outdoor compressor unit connected to an indoor fan coil unit. The indoor fan coil unit supplies air to ducts that condition a plurality of zones. Each zone has a volume modulating air damper that can maintain a predetermined volume of air flowing through it. As the dampers for some zones vary between open and close positions, the air pressure in the ducts changes. The volume modulating dampers compensate for these pressure changes, ensuring that only the predetermine volume of air is passing into the zones. By regulating the volume of into each zone, the volume modulating air dampers can restrict the air volume through the fan coil causing the outdoor unit to reduce compressor speed, thereby saving energy.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/832,798 filed Apr. 11, 2019 entitled Energy Savings Damper, whichis hereby incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Heating, ventilation, and air conditioning (HVAC) is a term thatgenerally refers to technology that maintains temperature comfort andacceptable air quality for indoor environments.

Two popular modern HVAC systems variable air volume VAV systems andvariable refrigerant flow VRF systems.

VAV systems are those that use dampers and thermostats to change theairflow rate to a room or zone but maintain the fan supplied airflow ata constant temperature. For example, a duct will supply air to a room at55 degrees Fahrenheit. The zone damper and room thermostat in this ductwill vary the cool air volume that reaches the room. A VAV system isvery efficient way to cool a plurality of rooms or zones in a buildingwhen full Compressor capacity and Fan capacity are required. Fullcompressor capacity is only required five percent of the year. The restof the year the compressor capacity is too great for the number of zonesthat require cooling. For example, in a system with a plurality of zoneswhen only a few zones require cooling both fan and compressor capacitymust be reduced.

To reduce fan pressure at full fan speed cooled system air is bypassedto the return side of the fan. Air volume that is not bypassed is sentto the duct system because only a few dampers are open. In this way thefan is using full energy when only a smaller amount of energy isrequired.

To reduce the compressor capacity when the leaving air temperature fallsbelow 55 degrees Fahrenheit the compressor is turned off for five ormore minutes. After this delay period the compressor is turned on. Thison off operation is costly because the refrigerant pressure has to beraised as much as 200 PSI. and inrush power to restart the compressormotor is very high.

A ductless VRF system typically circulates refrigerant through aplurality of evaporator fan coils. The airflow through these fan coilsis varied by a room thermostat that reduces the airflow as the roomtemperature approaches the thermostat set point.

As the airflow reduces an expansion valve in the fan coil reduces theamount of refrigerant flowing to the fan coil. Based on this reducedrefrigerant volume the compressor speed is reduced saving energy.

What is needed is an improved HVAC system that combines the efficienciesof VRF systems with VAV systems.

SUMMARY OF THE INVENTION

In one embodiment, an HVAC system is described having components of avariable refrigerant flow (VRF) outdoor compressor unit connected to aplurality of indoor fan coil units. The indoor fan coil unit suppliesair to ducts that condition a plurality of zones. Each zone has a volumemodulating air valve that can maintain a predetermined volume of airflowing through it. As the valves for some zones vary, the air pressurein the main duct changes. The volume modulating valves compensate forthese static pressure changes, ensuring that only the predeterminevolume of air is passing into the zones. By regulating the volume of airinto each zone, the volume modulating air valve can completely controlthe volume of air flowing through the fan coil and thereby reducecompressor energy of the outdoor unit.

In one embodiment, the volume modulating valves include a device fordetermining the air velocity passing through it. For example, a pitottube. The valves further include a motor to control a valve blade, and acontrol board to modulate the valve blade to achieve a target velocitybased on the velocity sensor readings.

In another embodiment, the present invention includes a method foroperating an HVAC system having an outdoor VRF unit, indoor fan coils, avolume modulating valve, and a thermostat. The volume modulating valvelimits the velocity of air passing through it so that the volume of airpassing into the zone can be known. By limiting the amount of airpassing through the indoor fan coil unit, the outdoor VRF unit canadjust its compressor and save energy.

Generally, the volume modulating air valves of the present inventionuniquely connect to a VRF system since the volume modulating air valvesprecisely measure the airflow through a VRF indoor fan coil which allowsthe VRF indoor fan coil to relay this information to the VRF outdoorunit. The outdoor unit increases or decreases refrigerant flow to theVRF indoor fan coil based entirely on the air volume.

Since the VRF indoor fan coil fan blows air into the duct system and allof the exits from the duct system have the volume modulating air valvesof the present invention, the only way for air to flow through the VRFindoor fan coil is for thermostats to open one or more of the volumemodulating air valves. Since the airflow through the volume modulatingair flow is relatively precisely known, the VRF outdoor unit canregulate the refrigerant to match the zones heating or cooling loads.Hence, on light load days heating or cooling energy is not wasted,similar to a system consisting entirely of VRF components.

In currently available VAV systems, the fan operates to deliver a fixedvolume of air (cubic feet per minute or CFM) at full cooling load. Asdampers in a VAV system close, less air is needed and excess air iseliminated by reducing fan RPM or bypassing air around the fan. Incurrently available VRF systems, three speed fans or a PID pulsed fanspeed may control Fan RPM.

In the system of the present invention, a discharge damper control iscreated using many volume modulating air valves. Each volume modulatingair valve, controlled by a thermostat, delivers a specifiedquantity/volume (CFM) of air to its conditioned space. A group of volumemodulating air valves automatically determine the total volume or numberof CFM's that can exit the fan coils duct system. These volumemodulating air valves form a variable discharge damper which controlsthe volume of air or CFM that leave or can enter the fan coils ductsystem. Therefore, no excess CFM are generated by the Fan. The Fan RPMdoes not need to be changed and no air needs to be bypassed.

This unique fan control system using volume modulating air valves togenerate a variable discharge damper is new to HAVC systems. It is alsoone of the reasons the system of the present invention worksefficiently. Ordinary dampers can't reliably do this job becausevelocity pressure changes will wildly change their air flow or CFM.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which:

FIG. 1 illustrates a traditional VRF system, as used in the presentinvention.

FIG. 2 illustrates an HVAC system using traditional VRF components andducted air components.

FIG. 3 illustrates another view of the HVAC system of FIG. 2.

FIG. 4 illustrates a side view of a volume modulating air valve.

FIG. 5 illustrates a front view of the volume modulating air valve ofFIG. 4.

FIG. 6 illustrates a flow chart for operating a volume modulating airvalve.

FIG. 7 illustrates a flow chart for operating the HVAC system of FIG. 2.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

The present invention is generally directed to an HVAC system that usesone or more volume modulating valves and a control system to measure anddeliver specific volumes of air. As described in greater detail below,by combining the volume modulating valves and control system tocomponents of a traditional VRF system, the present invention canemulate the operation of VRF indoor units as well as adjust thetemperature of a zone while reducing the complexity and costs associatedwith a traditional VRF system.

FIG. 1 illustrates an example overview of a traditional VRF system 10 inwhich multiple indoor fan coil units 14 are connected to a singleoutdoor VRF unit 12 via refrigerant lines 16. Each indoor fan coil unit14 typically includes evaporator coils through which the refrigerantpasses and a fan to blow air past the coils. Each unit 14 is typicallyinstalled in a zone 18 of a building and can be activated as necessaryto condition that zone 18. The outdoor VRF unit 12 determines thetemperature demands of the system based on the superheat temperature ofthe refrigerant and the volume of air passing through each indoor fancoil unit 14 and varies its compressor speed to adjust the refrigerant(or gas) temperature accordingly. This allows delivery of an appropriateamount of refrigerant to meet the temperature conditioning needs of theindoor fan coil units 14.

VRF systems 10 typically have improved energy efficiency over othersystems. However, their installation can be expensive, since each indoorfan coil units 14 are connected to long refrigerant lines 16, as well ascondensate drain lines. Further, since refrigerant lines 16 often havenumerous branch points, they provide risk of leakage.

FIGS. 2 and 3 illustrate an example HVAC system 100 of the presentinvention that combines aspects of a traditional VRF system 10 with airblown through a plurality of ducts 103 and 104. Instead of providing anindoor fan coil unit 14 in each zone 18, a single indoor fan coil unit14 can supply conditioned air to several different zones 18. Since theducts 20 for each of these zones 18 have volume modulating valves 102that are controlled to provide predetermined volumes of air, thetemperature for each zone 18 can be appropriately conditioned.

Each zone 18 preferably has its own thermostat 108 that is connected tothe volume modulating valve 102 supplying air for that zone 18. Eachthermostat 108 can be used to monitor the current temperature in a zone18 and send commands to the volume modulating valve 102 to allow passageof a predetermined volume of air (by measuring the air velocity). Sincethe volume modulating valves 102 are frequently opening and closingvarious amounts based on the temperature needs for a zone 18, the airpressure in ducts 103 and 104 may frequently change also. Without thevolume modulating valve, this would otherwise lead to more or lessvolume of air being unpredictably delivered from each vent 104A in eachzone 18 and can lead to each zone 18 changing temperature at anunpredictable rate. The volume modulating valves 102 constantly measurethe velocity of air passing through them and also constantly adjusttheir valve blade positions so that only a specific, determined volumeof air is being delivered to a zone 18. As discussed in further detailbelow, this allows for efficient operation of the indoor fan coil 14 andthe outdoor VRF unit 12.

It should be noted that part of the energy saving functionality of a VRFsystem 10 is the ability of the outdoor VRF unit 12 to adjust itscompressor to provide only the necessary refrigerant cooling (orheating) and pressure to the indoor fan coil units 14 instead ofconstantly running and/or starting and stopping. This allows the outdoorVRF unit 12 to adjust the compressor speed and refrigerant flow toprovide for only the needed amounts of cooling or heating. For example,refrigerant flow can typically be adjusted from its full volume down to35%. The goal is to keep the compressor running at the lowest level orspeed possible that still provides the appropriate cooling, with as fewon/off operations as possible. Shutting down the compressor causes therefrigerant pressures in the system to equalize and therefore requiresrelatively large amounts of pressure when started back up (e.g., 200pounds or more). Hence, lower, constant compressor speeds tend to bemore efficient than higher speeds with starts and stops.

The outdoor VRF unit 12 is able to adjust its compressor speed bymonitoring the temperature and superheat of the refrigerant. The speedat which the refrigerant heats up is dependent on how much air the fan14A passes through the evaporator coils 14B of the indoor fan coil units14 from the air return 19 (see FIG. 3). Generally, if more air passesover the evaporator coil 14B, the refrigerant warms more quickly(assuming the system is cooling the zones 18). If less air passes overthe evaporator coils 14B, the refrigerant warms less quickly (assumingthe system is cooling the zones 18). In a traditional VRF system 10 asin FIG. 1, the indoor fan coil units 14 can deliver cooling/heating to azone 18 at a relatively moderate rate. Slowing down the cooling processhelps reduce the speed that the compressor of the outdoor VRF unit 12must turn operate at, and thereby uses less power.

With reference to FIGS. 2 and 3, if the system 100 ONLY had traditionaldamper valves that fully opened and fully closed (i.e., no volumemodulating valves 102), it would not be able to perform the slower ormoderate cooling that a traditional VRF system 10 performs, causinghigher operating costs of its compressor and losing significant energyefficiency.

The reason for this is traditional dampers cannot measure the amount ofair passing through them. As more traditional dampers are closed, thestatic pressure and the velocity of air passing through the remainingopen dampers increases. For example, in FIG. 3, as the traditionaldampers for zones 18A and 18B are closed, more air will be forced out ofthe third traditional damper in zone 18C. Hence, the fan coil will seelittle change in air volume passing through it and the compressor of theoutdoor VRF unit 12 will not reduce speed to a lower power level. Putanother way, the fan coil will continue to pass the same amount of airwhen one traditional damper is open as when three traditional dampersare open, and therefore will require the same amount of cooling from theoutdoor VRF unit. This prevents the outdoor VRF unit from reducing itspower/operation level to a lower state and use less energy.

In contrast, the volume modulating valve 102 can deliver predetermined,measured volumes of air to a zone 18 (e.g., a specific cubic foot perminute requested by a thermostat). Returning to FIG. 3, if the volumemodulating valves 102 of the first two zones 18A and 18B are closed, theair passing through the third volume modulating valve 102 of zone 18Cwill not increase in speed, velocity, or static pressure because thatvalve 102 will then immediately adjust (e.g., close slightly) tomaintain the same volume of air passing through the vent 104A (i.e., bychanging the valve blade position). In that respect, the third zone 18Cwill continue to get the same volume of air into the zone 18 requestedby the thermostat 108.

As noted above, allowing the total amount of air passing through theindoor fan coil unit 14 to be reduced also reduces the cooling neededfrom the outdoor VRF unit 12, thereby reducing energy usage. The indoorfan coil unit 14 can become aware of the decreased air volume passingthrough it for managing the speed of the compressor in the outdoor VRFunit 12, since the indoor fan coil unit 14 typically monitors the airpressure within the ducts to maintain a preset external static airpressure. In this respect, the volume modulating valves 102 allow thepresent system 100 to have a similar energy efficiency as a traditionalVRF system 10.

FIGS. 4 and 5 illustrate a side view and an end view of one exampleembodiment of the volume modulating valve 102. In this example, thevolume modulating valve 102 has a tubular body 120 for connection totubular air ducts. However, it should be understood that other shapesare possible for connection to ducts of other shapes, such as rectangleor square.

The volume modulating valve 102 preferably includes an actuationmechanism, a command and communication mechanism, and a velocity sensingmechanism. The actuation mechanism can be in the form of a motor 126that is coupled to a shaft 124. The shaft 124 is fixed to valve blade122 (i.e., a flap) and therefore when the motor 126 rotates the shaft124, the valve blade 122 also rotates between an open and closedposition (i.e., between being oriented cross sectionally in the tubularbody 120 or perpendicularly to the cross section). Hence, the valveblade 122 can be not only fully opened and closed but positioned at anyorientation in between.

The velocity sensing mechanism of the volume modulating valve 102 can bein the form of one or more pitot tubes 132 that are connected to apressure sensor 130 that translates the pressure into a voltage and adigital velocity value. A single pitot tube 132 can be used, or as seenin FIG. 5, two or more pitot tubes 132 can be used to give an accuratevelocity reading for rectangular ducts or other shaped ducts.Additionally, other air velocity sensing mechanisms may be used.Preferably, the pitot tubes 132 open upstream of the valve blade 122.This allows for a velocity measurement of the air coming into the roomat a constant and known diameter/area (i.e., volume (CFM)=area (SquareFeet)×velocity (Feet per Minute). A velocity measurement, preferablyupstream of the valve blade, 122 will reflect the velocity after passingby the valve blade 122. It may also be possible to place the pitot tube132 immediately at a downstream interface of the valve blade 122, thoughthis may require determining the open area that the valve blade 132creates in various positions, which may be more difficult.

The command and communication system may include a microcontroller (orsimilar processing device) on a control circuit board 128 that isconnected to the pressure sensor 130 and the motor 126, thereby allowingit to read and store a pressure measurement (e.g., a voltage from thepressure sensor) and to modulate the valve blade 122 to various degrees(e.g., apply specific voltages to the motor). Additionally, themicrocontroller preferably includes a communication system that cancommunicate with the thermostat 108 (e.g., via a wired or a wirelessconnection).

FIG. 6 illustrates a flow diagram showing an example process forcontrolling the volume of the modulating valve 102. In step 150, thethermostat 108 determines that additional cooling or heating is neededand it transmits a target value to the volume modulating valve 102. Thistarget value can be, for example, 1) a target volume value, 2) a targetvelocity value, or 3) a potentiometer voltage or valve blade positionvalue. Other types of values are also possible, as long as thethermostat is able to send some type of data that can ultimately causethe regulation of air volume passing through the volume modulating valve102.

Depending on which of the three example target values are used for thetarget value, additional processing and conversion of that value willtake place. This processing can take place in the thermostat 108, in thecontrol circuit board 128, or some combination of the two where data isexchanged back and forth.

In example 1 of the target value mentioned above, the thermostat 108 mayinitially determine a desired volume of air that should be sent outthrough the volume modulating valve 102 and the microcontroller of thecontrol circuit board 128 can then calculate the desired target velocityset by the cool potentiometer, heat potentiometer, and ventpotentiometer. Dividing volume by the known area of the valve (i.e.,volume (CFM)=area (Square Feet)×velocity (Feet Per Minute). For example,a volume of 400 CFM divided by an area of 0.545 square feet (for a10-inch diameter valve) equals a velocity of 734 feet per minute.

Alternately in example 2 of the target value mentioned above, thethermostat 108 may already be aware of the diameter/area of the volumemodulating valve 102 and can calculate a target velocity that is thentransmitted to the control circuit board 128.

With regard to example 3 of the target value mentioned above, it is alsocontemplated that specific positions of the valve blade 122 can beassociated with known air volumes. A certain size volume modulatingvalve 102 for example, the control circuit board 128 or thermostat 108may include a table containing data on estimated air volumes with knownvalve blade positions and air velocities that have been previously setby the potentiometers. The thermostat 108 can send a Heat, Cool or Ventsignal to the control circuit board 128 and this signal uses the presettable voltage value set by the potentiometers. Thus, the thermostat 108can send this position value or the control circuit board 128 canconvert a requested target air volume into this position value.

As seen in step 152, once the target value has been converted to atarget velocity (at least for examples 1 and 2 above), the controlcircuit board 128 receives a pressure measurement value from thepressure sensor 130 and converts it to an air velocity within the volumemodulating valve 102 (or alternately directly receives a velocity valuefrom the sensor).

As seen in step 154, the control circuit board 128 then adjusts themotor 126 to move the valve blade 122 until that measured velocity valueequals the target velocity. For example, if the measured air velocitywithin the volume modulating valve 102 is lower than the targetvelocity, the motor 126 is activated to move the valve blade 122 towardsthe “open” position (e.g., in small increments or continuously) untilthe target velocity is reached. If the measured air velocity within thevolume modulating valve 102 is higher than the target velocity, themotor 126 is activated to move the valve blade 122 towards the “closed”position (e.g., in small increments or continuously) until the targetvelocity is reached.

Finally, in step 156, the measured air velocity is periodically checkedby the control circuit board 128 to confirm that it remains at thetarget velocity and the motor 126 can be adjusted if the measuredvelocity varies from the target velocity. In one example, the controlcircuit board 128 confirms that the measured air velocity equals thetarget air velocity periodically, such as every 1, 5, 10, or 15 seconds.As previously discussed, the static air pressure within the main duct103 will change as other volume modulating valves 102 open or close.Hence, by constantly monitoring that the measured air velocity matchesthe target air velocity, the target air volume will be maintained. Thistarget velocity is held until the control circuit board 128 receives anew target value from the thermostat (e.g., target velocity or targetvolume) or a command to completely close the valve blade 122 once theappropriate volume of air has been delivered.

Optionally, the volume modulating valve 102 may also includepotentiometers (e.g., 3) that are configured to convey the position ofthe motor 126 and valve blade 122. These potentiometers can beintegrated into the control circuit board 128 or can be separatelyconnected to the motor 126 or shaft 124 to relay data on the position ofthe valve blade 122 to the control circuit board 128. The controlcircuit board 128 can use predetermined potentiometer positions measuredby the pressure sensor 130 as starting points for the valve blade 122based on what the target value is. After moving to these “startingpoints,” the measuring and adjusting steps 152, 154, and 156 can beperformed. This can help get the valve blade 122 in a position toachieve a target velocity while allowing it to be more preciselyadjusted after the afore mentioned steps to exactly match the desiredtarget velocity. Alternately, this potentiometer can be used if thetarget value is a specific position of the valve blade 122 that waspreviously correlated with a known air volume.

With further regard to the use of the potentiometers, when a thermostatcalls for heat or cool (i.e., a target value), the volume modulatingvalve 102 stores or converts this target value to a potentiometervoltage. The volume modulating valve 102 then takes a reading of itssensor 130 and compares the sensor voltage. These analog voltages areconverted to digital counts by an analog to digital converter on thecontrol circuit board 128. The software of the control circuit board 128compares these counts. If the sensor count is higher than thepotentiometer count, the motor opens the valve slightly and reads thecounts again. If the sensor count is lower than the potentiometer count,the valve closes slightly and reads the counts again. This continuesuntil the target velocity is reached. The system operates in this manneruntil the room temperature reaches the target value. When the targetvalue is reached, the thermostat sends the volume modulating valve 102an instruction to operate in a vent mode which reduces the air flow to40% or less.

In an alternate embodiment, no potentiometers are necessary. When theroom temperature is above a set point, the thermostat sends digitaltarget value to the volume modulating valve 102. This target value callsfor full Heat or Cool air velocity. The target count is stored then thecontrol circuit board 128 reads the analog voltage of the sensor 130 andconverts it to from analog to a digital value. Just as in the analogversion, this digital value is compared to the target value and themotor opens or closes the valve blade 122 until the target voltage ismatched. In the cooling mode as the room temperature drops, a new lowervelocity target is sent to the volume modulating air valve 102. For eachdrop in temperature (e.g., two tenths of a degree), a lower velocitytarget is sent to the volume modulating air valve 102. When the roomtemperature drops one degree, reaching the set point, the thermostatholds the air delivery. This lower air velocity has a target value equalto the vent position in the Analog version.

Returning to FIGS. 2 and 3, a control unit 110 is connected/wired into alegacy thermostat interface attached to the indoor fan coil unit 14which allows the control unit 110 to switch the indoor fan coil unit 14into different modes of operation. Commonly, these modes are: a coolingmode to provide cool air, a heating mode to provide warm air, vent modeto circulate air without a temperature change, and an off mode thatprovides no heating, or cooling. The control unit 110 is also connected(wired or wireless) to each of the thermostats 108 that are supplied byan indoor fan coil unit 14, allowing the control unit 110 to monitor thecooling/heating needs of the thermostats 108 and set the operationalmode of the indoor fan coil unit 14 called for the by the control unit110.

In one example shown in FIG. 7, the control unit 110 determines the modeof the indoor fan coil unit 14 based on a voting-style algorithm. Instep 160, the thermostats each communicate their “vote” or request datafor cooling, heating, or neither (no vote) to the control unit 110 whereit is stored in memory. This can be a data message identifying thesending thermostat 108 and containing data that represents its requestfor cooling, heating, or no vote. Sending this “vote” data can be theresult of thermostat 108 being polled by the control unit 110 (e.g., thecontrol unit 110 sends out a request to the thermostats 108) or can betransmitted to the thermostats in a predetermined interval of time.

In step 162, the control unit 110 counts the vote data. This count mayoccur after receiving vote data for all thermostats 108 connected to thecontrol unit 110 or may occur after a predetermined period of time.Next, the control unit 110 determines which mode it should set theindoor fan coil unit 14 to based on which mode received the most votes,with a neither or no vote majority being in favor of the vent mode.While the cooling and heating modes are determined by a majority vote,the vent mode is determined by the thermostat 108 for each valve.

In step 164, the control unit 110 communicates with the indoor fan coilunit 14 to cause it to switch to the vote-determined mode. For example,the control unit 110 can energize a 24-volt legacy output to communicatethe vote-determined mode to the indoor fan coil unit 14. Once received,the indoor fan coil unit 14 automatically sets its fan speed based onthe total air volume of the valve and the outdoor VRF unit 12 operatesits compressor accordingly to circulate refrigerant through therefrigerant pipes 16.

With regard to the vent mode, when a thermostat 108 reaches its setpoint, the thermostat 108 sends a vent mode request to the volumemodulating air valve 102. In one example, the vent mode is less than 40percent of the cool or heat targets. This reduced volume of air keepsthe compressor of the outdoor VRF unit 12 running at a low speed. Thecompressor can reduce its speed as low as 30 percent, typically, so whenall but one of the volume modulating air valves 102 are in vent mode,the refrigerant will be reduced to its minimum circulation state. Whenall volume modulating air valves are in vent mode the control unit 110turns off the compressor.

Finally, the control unit 110 continuously polls (e.g., via pollingmessages) the thermostats 108 at regular intervals (e.g., every minuteor two minutes), which causes voting to occur again. This allows tocontrol unit 110 to switch modes on the indoor fan coil unit 14 ifnecessary.

Several other unique advantages of the present invention should benoted. For example, the air volume in the present invention iscontrolled without changing the fan speed of the indoor fan coil units14. In traditional indoor fan coil units 14, three speed fans are oftenused to limit airflow to the conditioned space and the units 14 aredesigned to run at full volume. In variable air volume systems, the fanis designed to run at full volume. When some dampers are closed, theexcess volume of air is bypassed around the fan/ducts. The presentinvention improves upon these inefficiencies.

It should also be noted that the present invention's ability to restrictand control fan/air volume without changing fan speed or RPM isinexpensive and efficient. Since the fan of the indoor fan coil unit 14controls the amount of refrigeration that the outdoor VRF unit 12 sendsto each indoor fan coil unit 14, the precise air volume control of thepresent invention allows the units 12 and 14 to operate efficiently.

While the system 100 is shown in FIG. 2 as having a single indoor fancoil unit 14, it should be understood that several indoor fan coil units14 can be connected to the outdoor VRF unit 12. In such an example, eachof the indoor fan coil units 14 may have their own ducts 103, 104,volume modulating air valves 102, thermostats 108, and control unit 110.Additionally, a system may further include additional indoor fan coilunits 14 used in their traditional manner to directly heat/cool a zone18 without air ducts.

While the volume modulating air dampener 102 is referred to as a valve,it may also be known as a damper.

While the system is described mostly as operating in a cooling capacity,it should be understood that it can also perform heating to zones aswell.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. An HVAC system, comprising: an outdoor VRF unitconfigured to supply coolant with a compressor; an indoor fan coil unitconfigured to receive coolant from the outdoor VRF unit; an air ductnetwork connected to the indoor fan coil unit; a plurality of volumemodulating air valves connected to the air duct network; and, aplurality of thermostats, each of which is connected to one of theplurality of volume modulating air valves; wherein each of the volumemodulating air valves are configured to 1) restrict passage of air tomatch a predetermined target volume for heating or cooling based oncommands from one of the plurality of thermostats and 2) enter a ventmode when a respective connected thermostat reaches a temperature setpoint; wherein the vent mode of each of the volume modulating air valvesmaintains an open state at 40% or less of the predetermined targetvolume for that respective thermostat; wherein the compressor of theoutdoor VRF unit maintains operation when at least one of the pluralityof volume modulating air valves is delivering the predetermined targetvolume for heating or cooling; and, wherein the compressor of theoutdoor VRF unit reduces operation to as low as 30% when at least one ofthe plurality of volume modulating air valves is delivering thepredetermined target volume for heating or cooling.
 2. The HVAC systemof claim 1, wherein each of the plurality of volume modulating airvalves comprise: a valve body having a passage therethrough; a closuremechanism within the passage configured to adjustably restrict passageof air through the passage; a motor connected to the closure mechanism;an air velocity sensor connected to the valve body and configured tomeasure an air velocity within the passage; and, a command andcommunication assembly comprising a processor connected to the motor andthe air velocity sensor; wherein the processor is configured to directthe motor to adjust the closure mechanism to maintain the predeterminedtarget air volume through the passage.
 3. The HVAC system of claim 1,further comprising a controller in communication with the plurality ofthermostats; the controller configured to connect to a thermostatinterface attached to the indoor fan coil unit and switch the indoor fancoil unit to different modes of operation; the controller beingconfigured to operate the indoor fan coil unit via the thermostatinterface based on voting messages sent from the plurality ofthermostats.
 4. The HVAC system of claim 2, wherein the closuremechanism is a valve blade that is rotatably mounted within the passage.5. The HVAC system of claim 4, wherein the motor is configured to rotatethe valve blade within the passage.
 6. The HVAC system of claim 2,wherein the air velocity sensor is a pitot tube.
 7. The HVAC system ofclaim 2, wherein the command and communication assembly furthercomprises a communication interface that is configured to communicatewith a thermostat and receive a target air volume value.
 8. The HVACsystem of claim 2, further comprising one or more potentiometers.
 9. TheHVAC system of claim 2, wherein the HVAC system is configured to:communicate a target value based on the predetermined target volume froma thermostats to one of the plurality of volume modulating air valves;measure an air velocity within a passage of the volume modulating airvalve to determine a measured air velocity; direct a motor to adjust aclosure amount of the volume modulating air valve until the measured airvelocity matches a target velocity based on the target value; and,maintain the measured air velocity at the target velocity by directingthe motor to adjust the amount of the volume modulating air valve asnecessary.
 10. The HVAC system of claim 9, further comprising a rotatingvalve blade within the air passage.
 11. The HVAC system of claim 9,further comprising measuring a voltage from a pitot tube sensorpositioned within the passage.
 12. The HVAC system of claim 9, whereinthe HVAC system is configured to: transmit heating or cooling requeststo a controller from a plurality of thermostats; the controller beingconfigured to operate the indoor fan coil unit based on the heating orcooling requests; determine a mode of operation with the controllerbased on the heating or cooling requests; and, change the indoor fancoil unit to the heating or cooling mode of operation with thecontroller.
 13. The HVAC system of claim 1, wherein each of the volumemodulating air valves comprises a valve blade and a potentiometerconfigured to sense a position of the valve blade; and wherein each ofthe volume modulating air valves are configured to move the valve bladeto a predetermined starting position based on the predetermined targetvolumes for heating or cooling and then further adjust the valve bladebased on a measured air velocity in each of the volume modulating airvalves.
 14. An HVAC system, comprising: an outdoor VRF unit configuredto supply coolant with a compressor; an indoor fan coil unit configuredto receive coolant from the outdoor VRF unit; an air duct networkconnected to the indoor fan coil unit; a plurality of volume modulatingair valves connected to the air duct network; and, a plurality ofthermostats, each of which is connected to one of the plurality ofvolume modulating air valves; wherein each of the volume modulating airvalves are configured to 1) restrict passage of air to match apredetermined target volume for heating or cooling based on commandsfrom one of the plurality of thermostat units and 2) enter a vent modewhen a respective connected thermostat reaches a temperature set point;wherein the vent mode of each of the volume modulating air valvesmaintains an open state at less than the predetermined target volume forthat respective thermostat; and, wherein the compressor of the outdoorVRF unit maintains operation when at least one of the plurality ofvolume modulating air valves is delivering the predetermined targetvolume for heating or cooling; wherein the compressor of the outdoor VRFunit reduces operation to as low as 30% when at least one of theplurality of volume modulating air valves is delivering thepredetermined target volume for heating or cooling.